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  • 1
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    Selection effects and binary galaxy velocity differences (1990)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Measurements of the velocity differences (delta v's) in pairs of galaxies from large statistical samples have often been used to estimate the average masses of binary galaxies. A basic prediction of these models is that the delta v distribution ought to decline monotonically. However, some peculiar aspects of the kinematics have been uncovered, with an anomalous preference for delta v approx. equal to 72 km s(sup-1) appearing to be present in the data. The authors examine a large sample of binary galaxies with accurate redshift measurements and confirm that the distribution of delta v's appears to be non-monotonic with peaks at 0 and approx. 72 km s (exp -1). The authors suggest that the non-zero peak results from the isolation criteria employed in defining samples of binaries and that it indicates there are two populations of binary orbits contributing to the observed delta v distribution.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA, Marshall Space Flight Center, Paired and Interacting Galaxies: International Astronomical Union Colloquium No. 124; p 485-490
    Format: application/pdf
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  • 2
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    Massive low surface brightness galaxies (1993)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: A multi-wavelength study of an extreme type of galaxy which will assist us in our attempts to understand the formation and evolution of galaxies was completed. In particular, a subset of low surface brightness (bar-mu(sub B) is approximately greater than 25 mag arcsec(sup -2)), giant galaxies (LSBG's) which contain large amounts of atomic gas (M(HI) is approximately greater than 10(exp 10) solar mass), have blue optical diameters similar to those of giant spiral galaxies, but which do not seem to have prodigious amounts of ongoing star formation were observed. Our sample was drawn from the first and second Palomar Sky Surveys. This population of galaxies has been largely ignored because of selection effects which make it difficult to detect optically. The question of how these massive systems differ from the higher surface brightness 'normal' spiral galaxies is addressed. Using B and R surface photometry, in conjunction with H-alpha, HI, CO-12, and far-infrared data, an attempt is made to determine if these galaxies had an early epoch of star formation that has since faded, have ongoing star formation with an unusual interplanetary magnetic field (IMF), or are perhaps galaxies which have never efficiently formed stars due to a lack of molecular clouds.
    Schlagwort(e): ASTROPHYSICS
    Materialart: NASA. Ames Research Center, The Evolution of Galaxies and Their Environment; p 84-85
    Format: application/pdf
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  • 3
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    An intelligent position-specific training system for mission operations (1992)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Marshall Space Flight Center's (MSFC's) payload ground controller training program provides very good generic training; however, ground controller position-specific training can be improved by including position-specific training systems in the training program. This report explains why MSFC needs to improve payload ground controller position-specific training. The report describes a generic syllabus for position-specific training systems, a range of system designs for position-specific training systems, and a generic development process for developing position-specific training systems. The report also describes a position-specific training system prototype that was developed for the crew interface coordinator payload operations control center ground controller position. The report concludes that MSFC can improve the payload ground controller training program by incorporating position-specific training systems for each ground controller position; however, MSFC should not develop position-specific training systems unless payload ground controller position experts will be available to participate in the development process.
    Schlagwort(e): CYBERNETICS
    Materialart: NASA-TM-108381 , NAS 1.15:108381
    Format: application/pdf
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  • 4
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    Luminosity function of quasars at large redshifts from grism surveys (1991)
    In:  Other Sources
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    Publikationsdatum: 2019-06-28
    Beschreibung: We have carried out a systematic search for emission-line objects through photometrically calibrated CCD grism surveys with the Palomar 200-inch telescope in transit mode, covering 62 square degrees. These surveys have yielded 141 quasars detected by their C IV or Ly-alpha emission in the redshift range 2.0 - 4.7. We use this sample and the known flux limits to derive the slope of the luminosity function and the space density above a given line luminosity, as a function of redshift. While space densities are approximately constant at redshifts 2.0 - 3.0, they are declining steeply for redshifts larger than 3.
    Schlagwort(e): ASTROPHYSICS
    Materialart: In: The space distribution of quasars; Proceedings of the Workshop, Victoria, Canada, June 3-5, 1991 (A93-28776 10-90); p. 109-114; Discussi
    Format: text
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  • 5
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    ControlShell: A real-time software framework (1994)
    In:  CASI
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    Publikationsdatum: 2019-06-28
    Beschreibung: The ControlShell system is a programming environment that enables the development and implementation of complex real-time software. It includes many building tools for complex systems, such as a graphical finite state machine (FSM) tool to provide strategic control. ControlShell has a component-based design, providing interface definitions and mechanisms for building real-time code modules along with providing basic data management. Some of the system-building tools incorporated in ControlShell are a graphical data flow editor, a component data requirement editor, and a state-machine editor. It also includes a distributed data flow package, an execution configuration manager, a matrix package, and an object database and dynamic binding facility. This paper presents an overview of ControlShell's architecture and examines the functions of several of its tools.
    Schlagwort(e): CYBERNETICS
    Materialart: AIAA PAPER 94-0890-CP , NASA. Johnson Space Center, Conference on Intelligent Robotics in Field, Factory, Service and Space (CIRFFSS 1994), Volume 2; p 870-877
    Format: application/pdf
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  • 6
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    The network data delivery service: A real-time data connectivity system (1994)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A network data-sharing system, the Network Data Delivery Service (NDDS), is discussed. The NDDS system relies on a bipartite model consisting of the following: information producers (sources) and information consumers (sinks). The example provided by a dual-arm robotic system is examined.
    Schlagwort(e): CYBERNETICS
    Materialart: AIAA PAPER 94-0889-CP , NASA. Johnson Space Center, Conference on Intelligent Robotics in Field, Factory, Service and Space (CIRFFSS 1994), Volume 2; p 591-598
    Format: application/pdf
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  • 7
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    The HST Quasar Absorption-Line Key Project. 8: CCD imaging of Hubble Space Telescope quasar fields (1994)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: We present an analysis of CCD images of more than 100 quasars; many of the objects have been or will be observed in the Hubble Space Telescope (HST) Key Project Quasar Absorption-Line Survey. The data set consists of B, g, and i photometry of 117 quasars and deeper g (limiting magnitude of approximately equal 22) images of 101 quasar fields. Positions accurate to approximately equal 1 sec, measured with the Space Telescope Science Institute's Astrometric Support Program, are listed for all of the quasars in this study. Positions, magnitudes, and classifications of stars and galaxies located within approximately equal 100 sec of the quasars are given for all of the deep g data. The positions of the stars and galaxies relative to the quasar are accurate to approximately equal 0.5 sec. The results presented here can be used to prepare spectroscopic programs designed to obtain redshifts of galaxies in the fields of these quasars.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 106; 700; p. 646-669
    Format: text
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  • 8
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    Northern dwarf and low surface brightness galaxies. II - The Green Bank neutral hydrogen survey (1992)
    In:  Other Sources
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    Publikationsdatum: 2019-07-12
    Beschreibung: The paper reports neutral hydrogen observations of a large sample of dwarf and other low surface brightness galaxies. A detailed discussion and error analysis of the observations are presented, and spectra are displayed for 329 galaxies detected for the first time, or detected with substantially better signal-to-noise ratios than achieved previously. The positions on the sky of 667 galaxies meeting the present selection criteria north of delta = 38 deg are shown. The distribution of the redshifts of galaxies detected at Green Bank is illustrated. The Green Bank detections tapered off strongly below the median H I flux of 3.7 Jy km/s detected at Arecibo: only 12 percent of the Green Bank sample was detected with smaller fluxes.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal Supplement Series (ISSN 0067-0049); 81; 1 Ju
    Format: text
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  • 9
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    Gravitational lensing of quasars as seen by the Hubble Space Telescope Snapshot Survey (1992)
    In:  Other Sources
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    Publikationsdatum: 2019-07-12
    Beschreibung: Results from the ongoing HST Snapshot Survey are presented, with emphasis on 152 high-luminosity, z greater than 1 quasars. One quasar among those observed, 1208 + 1011, is a candidate lens system with subarcsecond image separation. Six other quasars have point sources within 6 arcsec. Ground-based observations of five of these cases show that the companion point sources are foreground Galactic stars. The predicted lensing frequency of the sample is calculated for a variety of cosmological models. The effect of uncertainties in some of the observational parameters upon the predictions is discussed. No correlation of the drift rate with time, right ascension, declination, or point error is found.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astrophysical Journal, Part 1 (ISSN 0004-637X); 394; 1 Ju; 51-60
    Format: text
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  • 10
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    A gravitational lens candidate with an unusually red optical counterpart (1992)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: The properties of the strong radio source MG0414 + 0534 are described. It is found to display many of the properties expected in a gravitational lens system. At radio wavelengths and 0.5-arcsec resolution, MG0414 + 0534 is made up of four compact components whose unusual configuration and relative flux densities are similar to those found in confirmed four-image gravitational lens systems. At optical wavelengths three objects are detected, consistent with there being optical objects at the positions of the radio components, given the lower optical resolution. The radio and optical centroid positions agree within the astrometric errors, and the relative ordering of the fluxes is the same. The colors and radiooptical spectral indices are similar, but there are differences larger than the photometric errors and the measured variability (about 30 percent). Extinction by dust might simultaneously explain the unusually red color and the absence of light from a lens.
    Schlagwort(e): ASTROPHYSICS
    Materialart: Astronomical Journal (ISSN 0004-6256); 104; 3 Se; 968-979
    Format: text
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